Overexposure to UVA and UVB rays from the sun can cause many problems such as wrinkling, premature aging, sunspots, and even the deadliest form of skin cancer, Melanoma. Many people are unaware of when they have become overexposed.
Clothing does not prevent UV rays from reaching the skin and causing damage. A white shirt has the SPF of about 7, when wet the protection offered drops to about 3. One way to detect if a piece of clothing fully protects a person is holding it up to the sun, if any light goes through it can still be harmful. Any person, especially a child, is susceptible to the damage of the sun's UV rays. 10% of the work force in the United States work outdoors.
People that spend time on the beach need to be extra careful of their exposure to the sun's UV radiation. Even when in shade, sand can reflect roughly 17% of the sun's UV rays. Also, even when living in areas where there is relatively little Sunlight, the UV rays can still damage skin year-round. UVB rays cause sunburn and are the most noticeable, but both UVA and UVB rays can penetrate through clouds, so even on a cloudy day the sun can be very harmful to the skin. Furthermore, residing or spending time in areas with snow, it is a common necessity to use broad-spectrum sunscreen because snow reflects roughly 80% of the sun's UV. Reflected UV rays have a cumulative effect on the damage afforded to a person.
UVA rays can be harmful even indoors. UVA rays penetrate through glass allowing them to be harmful even when indoors. In limited quantities, UVB rays can be beneficial to life, for example in the intake of Vitamin D, however overexposure can be very harmful to humans, especially as the ozone layer gets more depleted more UVB rays penetrate and reach ground level and create greater harm.
People have limited knowledge or sense of their exposure to UVA and UVB rays. The ever-changing weather patterns, the constant moving from shade, to sunny areas, and time spent indoors compared to outdoors, make determining one's exposure to UVA and UVB rays almost impossible.